Colorimeter probe



y 21, 1968 D. F. GIBSON COLORIMETER PROBE 2 Sheets-Sheet 1 Filed March24, 1964 INVENTOR. 004 41 0 E A830 aAp 4 v'ra Elk 52 3 May 21, 1968 D.F. GIBSON COLORIMETER PRQBE Filed March 24, 1964 2 Sheets-Sheet 2-:

INVENTOR. DO/VAZO F: 6/ 8 MJ/XZZ United States Patent 3,383,979COLORIMETER PROBE Donald F. Gibson, Billerica, Mass., assignor to MarkAssociates, Inc., Lowell, Mass. Filed Mar. 24, 1964, Ser. No. 354,484 4Claims. (CI. 88-14) ABSTRACT OF THE DISCLOSURE A miniature probe formeasuring the color and light intensity of a subject. The probe has anopaque outer surface and an elongated cylinder which houses a lightsource, light guide and the photovoltaic cell and which can be held inones hand during the operation thereof.

The invention described herein may be manufactured and used by or forthe United States Government for governmental purposes without paymentto me of any royalty thereon.

This invention pertains generally to instruments for measuring andcom-paringcolor, and in particular, to a miniature probe therefor.

Measurements and comparisons of color naturally will vary with differentlight sources. Heretofore, colorimeters required the test subject to beplaced in a space Where the light source could be controlled. This maynot always be convenient nor possible, and therefore, it is desirable tohave a portable device capable of accurate color testing in the presenceof environmental light without regard thereof.

Thus, it is an object of this invention to perform accurate color testson a subject without regard to environmental light thereabouts.

It is an object of this invention to provide a compact and portablecolorimeter.

Another object is to provide a miniature and portable probe forcolorimeters.

A further object is to provide a colorimeter probe that is convenientand simple to use and which is capable of yielding individual readingsas well as a composite reading for separate areas of the test subject.

It is still another object of the invention to provide a colorimeterprobe which is economical to produce and which utilizes conventional,currently available components that lend themselves to standard massproduction manufacturing techniques.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims taken in conjunctionwith the accompanying drawings, in which:

FIGURE 1 is a schematic cross-section of the invented colorimeter probe;

FIGURE 2 is an exploded perspective representation of FIGURE 1; and

FIGURE 3 is a simplified circuit diagram for the invented probe.

With reference to the figures, wherein like numerals refer to likeparts, the probe is generally an elongated cylinder enabling it to beheld in the hand against a test subject 12. As illustrated, the cylinderincludes an opaque outer surface which tapers to the test port 18 at oneend of the probe 10. Port 18 admits the passage of light axially intothe probe 10, however, notice that port 18 is enclosed from externallight by surface 15 and subject 12 whenever the probe 10 is held againsta test subject 12 as shown in FIGURE 1. Port 18 is shown as circular inshape, however, other shapes and sizes may be employed to accommodate aspecific subject. For example, a form fitting rectangular shape may beutilized for color testing of human teeth.

A light guide is provided within probe 10 by an opaque "ice tubularsurface 25. The light guide is concentrically positioned within probe 10and leads to the center of port 18. As shown, tubular surface 25 may bea series of tubular surfaces decreasing in diameter toward port 18, toprovide a light source thereat smaller than the port 18.

A controlled source of light is provided within the light guide by bulb27 and an adjustable current supply 29, utilizing conventional circuitryand available components.

Photovoltaic cells 35 are of known sensitive type, and sufficientlyminiature for placement within probe 10 proximate the port 18. Asiflustrated in FIGURE 3, the cells 35 are affixed symmetrically aroundthe light guide between the opaque surfaces 15, 25, at a position toreceive reflections from subject 12, the opaque surfaces screening outall extraneous light. A tristim-ulus filter 36 is inserted into thelight guide to be between the bulb 27 and port 18,

As indicated at FIGURE 2, the probe may have a separate nose block 11constructed of a transparent material, such as glass or a clear plastic.In this case, the cells 35 and leads 38 are cast within the block 11 tofirmly affix them in position. The block 11 is appropriately shaped andbored therethrough to provide a light guide. The opaque surfaces 15 and25 may be provided by a covering film such as an opaque paint or byother wellknown methods.

Suitable wires 38 connect the cells 35 to a switching circuit 40,leading to the external current measuring indicator 50. It is preferablethat leads 38 be flexible for portions outside the probe 10. Forpurposes of illustration, a simplified switching circuit is shown inFIGURE 3, including a conventional indicating meter 50 and multipositionswitch 45.

During a test, the probe 10 is held against a subject 12, and noconsideration need be given to the external light thereabouts. In thecase of a liquid or powder subject 12, the probe 10 is immersed into thesubject. .Light travels from bulb 27, in direction of arrows, to thesubject 12. Cells 35 receive light reflections from subject 12 andproduce a proportional current output which registers on mete-r 50. Withswitch 45 in position 1, only cell 35a is activated, and a reading willregister for only that area of subject 12 opposite cell 35a. Positions 2and 3 activate cells 35b, 35c and 35d, respectively, for readings ofrespective opposite areas. Position 4 yields a composite reading withall the cells activated, The relative percentage present of the threeprimary colors may be measured by insertion of standard tristimulusfilters 36 and the readings thereof recorded.

Although the invention has been described with reference to a particularembodiment, it will be understood to those skilled in the art that theinvention is capable of a variety of alternative embodiments within thespirit and scope of the appended claims.

I claim:

1. A miniature probe for measuring color and light intensity of asubject, comprising: an elongated cylinder including an opaque outersurface and having a test port at one end to be held against saidsubject, said outer surface and subject enclosing said port fromexternal light; a light guide concentrically within said cylinder formedby an opaque tubular surface leading to said port; alight source withinsaid guide directing light to said port; a photovoltaic cell affixedwithin said cylinder proximate said port and without said guide inposition between said opaque outer and tubular surfaces to receive onlyreflec tions of said source from said subject, said opaque surfacesscreening extraneous light therefrom; and flexible electrical leadsextending from said cylinder to connect said cell to an indicatingmeter.

2. The invention according to claim 1 wherein said light guide is formedby a series of tubular surfaces, decreasing in diameter toward saidport.

3. A miniature probe for measuring color and light intensity of asubject, comprising: an elongated cylinder including an opaque outersurface tapering to a test port at one end to be held against saidsubject, said port shaped to accommodate said subject, and said outersurface and subject enclosing said port from external light; a lightguide concentrically within said cylinder formed by an opaque tubularsurface leading to center of said port; a controlled light source Withinsaid guide directing light to said port center; a plurality ofphotovoltaic cells affixed Within said cylinder proximate said port andsymmetrically around said guide in position between said opaque outerand tubular surfaces to receive only reflections of said source fromsaid subject, said opaque surfaces screening extraneous light therefrom;switching means to enable said cells to act singularly and jointly, asdesired; and flexible electrical leads extending from said cylinder toconnect said cells and switching means to a current measuring indicator.

4. The invention according to claim 3 having a tri stimulus filterinsert within said guide between said light source and port.

References Cited UNITED STATES PATENTS 2,269,813 1/1942 Garity et al.88-14 2,406,166 8/1946 Scott 8814 2,420,716 5/1947 Morton et al. 250-2272,710,924 6/1955 Morrison et al. 8814 2,936,886 5/1960 Harmon 8'8143,130,317 4/1964 Connolly et a1. 250-227 3,305,689 2/1967 Leavy, et al.250227 3,306,157 2/1967 Hach 8814 2,843,112 7/1958 Miller 88-143,327,583 6/1967 Vanderschmidt et al. 8814 JEWEL-L H. PEDERSEN, PrimaryExaminer.

W. A. SKLAR, Assistant Examiner.

